There are many techniques for connecting the ends of two lengths of metal pipes, conduit or tubing (hereinafter sometimes collectively referred to as “tubing”). The essence of the invention relates to providing full-strength structural connection between two pieces of metallic tubing or piping. In this connection, full-strength structural connection refers to developing the full capacity of the joined adjacent tubing in compression, tension and bending. Such connections are required in construction. While the invention is primarily intended to be used in connection with the joining of similar external and internal-diameter pipe or tubular segments, the technology disclosed herein can be put to use in connection with joining metal piping or tubular segments with the same external diameter or dimension (in the case of non-circular piping) but different wall thicknesses (thus different internal diameters or dimensions). Furthermore, the present invention is not restricted to its potential use in wholly tubular structures, for example, it is also capable of being employed in connection with trusses having rolled-section chords and tubular bracing members. However for ease of understanding, the invention will be described in connection with round pipes and tubing, it being understood by the reader that the same concept and invention can be employed in connection with square, rectangular or other shaped tubing or piping. Clearly, however, the portion of the device which is in contact with the outside wall of the tubing must conform and be laid upon the dimension and shape of the tube/piping sought to be joined. For illustration purposes, the invention is principally shown and described in connection with round pipes to be joined and, yet, is illustrated in connection with coupling a pair of square-shaped pipes, in FIG. 5.
Among the unique features of the invention, apart from its ability to provide a full-strength connection in compression, tension and bending are: all welding is carried out at the location of fabrication; all welding consists of simple downhand fillet welds; no site welding is required; site assembly requires only the installation of the connecting nuts and bolts; the loading of the joint, whether it be compression, tension or bending, applies only shear forces to the fillet welds, the preferred action; the loading of the joint, whether it be compression, tension or bending, applies only shear forces to the bolts, again the preferred action; the coupling pieces can be orientated in any direction to facilitate subsequent assembly (this is particularly useful in the case of trusses having tubular bracing members); and in comparison to conventional flange plate connections, the present invention provides significantly greater tolerance in “fit-up” requirements.
As an example of the prior art, U.S. Pat. No. 2,326,941 discloses joints for demountable steel structures, in which the ends of the pipes are enlarged and the couplers are provided with grooves to accept the enlarged ends of the tubes. This requires modification to the normal constant cross-section of the tubes. The approach of this reference involves the sealing off of the ends of the tubes. The present invention, on the other hand, develops the full-strength structural connection between the open-ended tubes in that the full capacity of the adjacent tubes in compression, tension and bending are developed. Also, the integrity of the joint shown in the '941 patent depends largely on the clamping action of the two half-shells 15 holding together the flanges. Further, these half-shells 15 are fairly expensive machined or forged cast pieces, and are typically required to be much thicker and stronger than the tubes themselves. The present invention, on the other hand, is expected to have the welding performed in the fabrication facility, and thus there will be no need for on-site fabrication.
FIG. 4B of the present disclosure illustrates a prior art flange plate 70. FIG. 4A illustrates pipes 30 and 40 connected via two plates of the type of prior art flange plate 70 shown in FIG. 4A, by bolting the flange plates 70, illustrated using bolt locations 71, 72 etc. It can be easily appreciated that the bolts extend along the axial length or direction as the tubular sections and the flanges are secured to the ends of the tubular sections by welding which extends circumferentially around the tubular sections. The fillet welding of the present invention, however, extends along the axial direction of the tubular sections and the bolting of the flanges, as described herein and illustrated in the drawings of the present invention, extend across the longitudinal direction of the tubular segments.
The prior art cast metal or machined flange plates entail more expense, and may involve a bulkier coupling because the flange plates extend radially out from the pipes 30 and 40.